20,063 research outputs found

    Groupoid Approach to Quantum Projective Spaces

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    We show how the C*-algebras of quantum complex projective spaces (standard or nonstandard) are related to groupoids.Comment: 12 page

    The Structure of Line Bundles over Quantum Teardrops

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    Over the quantum weighted 1-dimensional complex projective spaces, called quantum teardrops, the quantum line bundles associated with the quantum principal U(1)-bundles introduced and studied by Brzezinski and Fairfax are explicitly identified among the finitely generated projective modules which are classified up to isomorphism. The quantum lens space in which these quantum line bundles are embedded is realized as a concrete groupoid C*-algebra

    S-Lemma with Equality and Its Applications

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    Let f(x)=xTAx+2aTx+cf(x)=x^TAx+2a^Tx+c and h(x)=xTBx+2bTx+dh(x)=x^TBx+2b^Tx+d be two quadratic functions having symmetric matrices AA and BB. The S-lemma with equality asks when the unsolvability of the system f(x)<0,h(x)=0f(x)<0, h(x)=0 implies the existence of a real number μ\mu such that f(x)+μh(x)0, xRnf(x) + \mu h(x)\ge0, ~\forall x\in \mathbb{R}^n. The problem is much harder than the inequality version which asserts that, under Slater condition, f(x)<0,h(x)0f(x)<0, h(x)\le0 is unsolvable if and only if f(x)+μh(x)0, xRnf(x) + \mu h(x)\ge0, ~\forall x\in \mathbb{R}^n for some μ0\mu\ge0. In this paper, we show that the S-lemma with equality does not hold only when the matrix AA has exactly one negative eigenvalue and h(x)h(x) is a non-constant linear function (B=0,b0B=0, b\not=0). As an application, we can globally solve inf{f(x)h(x)=0}\inf\{f(x)\vert h(x)=0\} as well as the two-sided generalized trust region subproblem inf{f(x)lh(x)u}\inf\{f(x)\vert l\le h(x)\le u\} without any condition. Moreover, the convexity of the joint numerical range {(f(x),h1(x),,hp(x)): xRn}\{(f(x), h_1(x),\ldots, h_p(x)):~x\in\Bbb R^n\} where ff is a (possibly non-convex) quadratic function and h1(x),,hp(x)h_1(x),\ldots,h_p(x) are affine functions can be characterized using the newly developed S-lemma with equality.Comment: 34 page

    Response to Comment on “Characterization of Excess Electrons in Water-Cluster Anions by Quantum Simulations”

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    In response to the Comment by Neumark and co-workers, we reiterate that the conclusions of the title Report are based on identifiable characteristic trends in several observables with cluster size. The numerical comparison between simulated and experimental vertical detachment energies emphasized in the Comment reflect quantitative limitations of our atomistic model, but, in our opinion, do not undermine these conclusions
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